The invention relates to a leg prosthesis comprising an artificial knee joint having swing phase control and recoil brake wherein a control member provided at the knee joint controls the knee joint depending on control signals based on a viscosity change of a magneto-rheological liquid.
When walking with a prosthesis the thigh member is moved forward by the residual limb. The leg member may, owing to its mass inertia, bend back very far if the damping is not properly adjusted. The wearer of the prosthesis then has to wait until the prosthesis moves again in forward direction before putting the foot on the ground. This results in an unharmonious walking appearance, an unfavourable time characteristic and therefore poor wearing properties.
It is known to provide leg prostheses comprising an artificial knee joint with a damping member formed as a pneumatic or hydraulic cylinder for swing phase control and as a so-called recoil brake. The leg prosthesis is adapted to the wearer by means of a stationary walking pattern analysis system. The wearer of the prosthesis must do a test run, for example on a walking band, and the walking pattern is then subjectively evaluated by an orthopedic technician.
Taking also the subjective sensations of the wearer of the prosthesis into account, the various components of the prosthesis are then adapted and adjusted. The result of this adjustment is often inaccurate because it is based on subjective criteria. Further, later changes such as weight changes, temperature changes or changes of the ground conditions are not taken into consideration.
Moreover, the known damping members for artificial knee joints are disadvantageous in that they are unable to react in a sufficiently fast manner to an abrupt change of the walking dynamics.
It is the object of the invention to provide a leg prosthesis comprising an artificial knee joint with a swing phase control and a recoil brake, the leg prosthesis ensuring an always optimum operation which is adapted to the wearer as well as fast reaction to abrupt changes of the walking dynamics.
This object is achieved by a control based on a viscosity change of a magneto-rheological liquid and an automatic control producing control signals on the basis of detected values to automatically regulate the knee joint functions during the operation of the prothesis.